ANTHRACNOSE OF LUPINS

Note: This disease is present in Western Australia and South Australia, but not Victoria.

Introduction

Anthracnose, caused by the fungus Colletotrichum lupini, is a highly destructive disease of lupins. The disease can cause complete crop losses in susceptible varieties. anthracnose was first detected in Western Australia and South Australia in lupin crops in 1996 but the disease has not been detected in Victoria to date. Lupin growers and commercial agronomists are urged to monitor lupin crops for this disease.

What to Look For

Anthracnose lesions can form on all above-ground parts of the lupin plant. The most distinctive symptom is the bending and twisting of stems with a lesion in the crook of the bend. This is particularly noticeable when the crop is flowering. Stem lesions are usually dark brown and elongated up to about two centimetres in length. A pale pinkish (sometimes orange) spore mass develops within lesions, (Figure 9.8).

The stem is often completely girdled by these lesions or weakened so that it breaks. Both the main stem and lateral branches can be affected and close inspection will often show similar symptoms on leaf petioles. Leaf lesions are not numerous but may be seen as beige spots with a dark brown border.

Pods develop lesions similar to stems and are often twisted and distorted. Pod infections can result in complete loss of pods or production of infected seed. Infected seeds can be malformed, have brown lesions, fungal mycelium on the seed surface, or have an occasional pink spore mass, (Figure 9.9). Seeds can also be anthracnose infected without any visible symptoms.

Figure 9.8 Albus lupin affected by anthracnose. Note dark stem lesions with bright spore masses, and crooking of stem (Image courtesy DAFWA, www.agric.wa.gov.au)

Figure 9.9 Lupin seed infected with anthracnose (Image courtesy DAFWA, www.agric.wa.gov.au)

Disease Cycle

The disease survives on old lupin trash, as well as in or on infected seed. The pathogen will not survive in the soil in the absence of stubble residue.

The fungus can survive for up to two years on infected seed. Infected seed that is sown will produce infected seedlings which will quickly produce lesions on the root, hypocotyl, cotyledons, leaf petioles or stems, (Figure 9.10). These lesions produce an abundance of spores that can be splashed onto surrounding plants by rain and establish the disease in a new crop, (Figure 9.11).

Small amounts of the fungus can survive over summer on infected stubble. Rain stimulates the pathogen and spores produced on the old stubble can infect new crops through rainsplash.

Figure 9.10 Anthracnose seedling infection (Image courtesy DAFWA, www.agric.wa.gov.au)

Figure 9.11 Myallie lupins infected with anthracnose. Note; characteristic bending and twisting of stems (Image courtesy DAFWA, www.agric.wa.gov.au)

Management

Do not move vehicles or equipment from an infected paddock to uninfected areas without thoroughly washing them down. If you walk through an anthracnose infected lupin crop, wash all clothing and sterilize hands and boots by spraying with commercial bleach (2 per cent). Early detection can assist in containment of the disease if found. Growers should closely monitor all of their lupin crops for symptoms of anthracnose

Seed Selection

Sowing clean seed is the best management tool for avoiding crop infection. Avoid seed from South Australia and Western Australia where anthracnose is known to occur. A commercial seed test is available from AGWEST plant laboratories, Western Australia (Ph 08 9368 3721).

Paddock Selection

Ensure at least a two-year break (preferably longer) occurs between lupin crops within the same and adjacent paddocks.

Varietal Resistance

Growers are advised to select varieties with moderate resistance (Table 9.1). All varieties of albus lupin are considered highly susceptible. Avoid planting Russell lupins. Ornamental or Russell lupins have been found to carry anthracnose in some instances. These lupins should not be grown in gardens on properties where lupins are grown. Varieties of narrow leaf lupins differ in their susceptibility to anthracnose.

Fungicides

Disease transmission from infected seed can be reduced with the use of a fungicide seed dressing.

Further Information

More detailed information can be obtained from the DEDJTR AgNotes Series www.vic.gov.au/ graindiseases

Victorian Pulse Diseases Guide www.vic.gov.au/ pulsediseaseguide

Victorian Winter Crop Summary www.vic.gov.au/ victorianwintercropsummary

Seed Health Testing in Pulse Crops (AG1250) www.vic.gov.au/seedtestingpulsecrops

Pulse Seed Treatments and Foliar Fungicides http://www.pulseaus.com.au/storage/app/media/ crops/2011_APB-Pulse-seed-treatments-foliar- fungicides.pdf

Pulse Australia www.pulseaus.com.au

 

PHYTOPHTHORA ROOT ROT OF LUPINS

Lupin disease reaction tables/guides